PORT ST. LUCIE — Dave Eiland was one happy man. On a back field at 10:30 in the morning, the Mets’ pitching coach had stood behind Jacob deGrom and watched him lock up hitters in a simulated game with his usual dominance and not a hint of a back problem.

So now Eiland was feeling good, talking to reporters afterward, saying it is still to be determined when deGrom will throw next — could be in four days rather than five, depending how he feels after throwing 30 pitches Tuesday morning.

If it’s four, then deGrom would pitch in Tampa against the Yankees, and so Eiland was asked if he’d be concerned about a three-hour bus ride for a pitcher just getting over lower back stiffness.

“He can go the night before,” Eiland said without hesitation. “He can stay at my place. I’ll drive him to my house — it’s about 20 minutes north of that stadium. I’ll make sure he gets a good dinner. My wife will cook for him.”

By now reporters were giggling and the pitching coach’s smile was widening with every word.

“He can use my bed,” he continued. “My wife and I will go sleep somewhere else, and we’ll make sure he’s comfortable. If we decide he can pitch on his fourth day.”

OK, Eiland may have been having a little fun with his answer, but I don’t doubt that he would make good on his offer. He’s a much better pitching coach, after all, with a healthy deGrom dealing every five days.

For that matter, the truth is the Mets desperately need deGrom if their starting rotation is going to return to anything resembling the brilliance of their World Series season in 2015.

Until proven otherwise, he and Noah Syndergaard are the only two starters the Mets can bank on to be elite, as all that talk of an all-time great rotation feels older these days than Bartolo Colon.

That’s not to say that Eiland and manager Mickey Callaway are lying when they talk about how impressed they are by the number of power arms the Mets can boast, as they have been since spring training opened.

Jacob deGrom's successful simulated game Tuesday has Dave Eiland and the Mets feeling better about their rotation.

(Jeff Roberson/AP)

After calling deGrom “an unbelievable talent,” in fact, Eiland felt compelled to offer a similar compliment about his other starters.

“From a pitching coach’s standpoint,” he said, “it’s very exciting to have a group like we have.”

The problem, of course, is all the scar tissue, both mental and physical, that makes predicting success in 2018 such a dicey proposition.

Matt Harvey is showing progress, but he’s a long way from proving he’s back to even being a reliable starter; Zack Wheeler’s stuff has looked good, but his injury-shortened total of 86 innings last season are all he’s thrown since 2014.

And then there’s Steven Matz. The Mets say the oft-injured lefty has wowed them with his bullpens, yet he hasn’t been able to work out of trouble in either of his first two starts.

So what’s the issue? On Tuesday Callaway told me he believes it’s mostly a mental hurdle.

“It’s just a matter of conviction,” the manager said. “I think he’s worried about the result instead of just committing to the pitch and letting it go.

“After the outing the other day, he mentioned that nobody wants to get hit even in spring training. Well, he gave up a bloop, he gave up a roller. It was the command, it was the walks that were the problem.”

Callaway said that fear of contact is messing with Matz’s delivery, to some degree:

Dave Eiland and Mickey Callaway know how important Jacob deGrom's health is to the Mets' potential success.

“He’s tracking his pitches so he’s standing up and yanking (his arm) instead of following through. But he’ll be fine. I had the same ulnar nerve transposition surgery that he had, and it takes time to get your feel back.

“He’s looked great in his side sessions. He’s just gotta feel that batter in there. It’ll take one good outing and it’ll start clicking for him.”

That makes sense, and Callaway makes similar cases in projecting success for Harvey and Wheeler this season. But until proven otherwise, it’s really just hope and faith.

Which is why deGrom’s simulated game drew quite a crowd of luminaries among the Mets’ hierarchy to watch. Even former manager Terry Collins, who spends his days here overseeing the workouts of minor-leaguers, made a point of wandering over to get an up-close look.

And deGrom didn’t disappoint. Nobody had a radar gun on him, but he was overmatching Juan Lagares, Dom Smith and Tim Tebow with his fastball, as well as mixing in off-speed stuff that froze hitters in place.